American anti-ballistic missile evolved from the Nike Zeus and designed to intercept ICBM warheads in space. Three stage vehicle consisting of 1 x TX-500 + 1 x TX-454 + 1 x TX-239 solid propellant motors. Nearly as large and just as costly as the missiles it was designed to intercept. After 20 years of development, deployment was limited by arms agreements, and 30 were only briefly in service in 1975-1976.

In September 1967, the unaffordable Nike-X program for comprehensive anti-ballistic missile protection of the United States was cancelled and replaced by the thinner and more affordable Sentinel system. This was in turn replaced by the even more affordable Safeguard in 1969, designed only to protect ICBM fields and Washington DC. At the time of Sentinel the evolved Nike Zeus missile was renamed Spartan. First launch was in March 1968, and Spartan achieved its first intercept of a Minuteman ICBM in August 1970. However 1972 arms limitation negotiations with the Soviet Union allowed each side only one ABM site with 100 missiles. Accordingly, on 1 October 1975, a single Safeguard ABM site with 30 Spartan and 70 Sprint missiles went on-line in North Dakota. It was ordered deactivated by the US Congress the next day, and closed six-months later, ending America's first thirty-year effort to obtain a ballistic missile defense system.

Spartan was an all-solid propellant, command guided missile nearly as large and costly as the ICBM's it was built to intercept (this was a major argument against it – the adversary could always counter it by building more ICBM's at less expense than the multiple ABM's necessary to kill them). Spartan's specialized W71 thermonuclear warhead was tuned to use neutron flux to disable the nuclear warheads of incoming enemy missiles.

Western Electric-McDonnell-Douglas LIM-49Nike Zeus-SpartanOn 18 September 1967, the Nike-X was cancelled and replaced by a system called Sentinel, which was to be a much thinner (and therefore cheaper!) ABM defense shield. At the same time, Nike Zeus EX was renamed Spartan, and the prime contract was now shared between Western Electric and McDonnell-Douglas. The Spartan missile received the designation LIM-49A. The short-range, endo-atmospheric missile component of Sentinel was the Martin Orlando Sprint.

The LIM-49A Spartan was stored in and launched from underground silos, and the first Spartan launch occured in March 1968. In August 1970, an LGM-30 Minuteman RV was intercepted for the first time. In 1969, however, the Sentinel system had been cancelled, and replaced by Safeguard, an ABM system planned to defend only SAC's ICBM bases, and not the cities of the United States. The SALT I treaty of 1972, and a 1974 addendum, limited even this to one site with 100 ABMs. On 1 October 1975, the U.S.'s one and only Safeguard ABM site became operational with 30 Spartan and 70 Sprint missiles. However, because the very limited defense offered by a single ABM site did not warrant the costs, the site was deactivated by Congress the next day.

The designations of the various Nike Zeus, Nike-X and Spartan missiles are a bit confusing. Many sources say that the Nike Zeus A received the designation XLIM-49A in 1963, although development had stopped in 1960, and Nike Zeus B became XLIM-49B, although it had almost nothing in common with the XLIM-49A. However, the Department of Defense document [3], which is the "official" list of DOD aircraft and missile designators, describes the XLIM-49A as a three-stage intercept missile. Unfortunately, the name is given as Nike Zeus, without an A or B suffix, but "three-stage" clearly points to the Nike Zeus B. If this is true (and why shouldn't it), the designation LIM-49A for the Spartan would make a lot more sense, because Spartan was indeed a modified-improved Zeus B, but had nothing in common with the Nike Zeus A. Zeus A itself had received no designation in this case, which is quite logical, because it didn't exist anymore in 1963.

Further adding to the ABM designation confusion is that all my sources say the short-range Sprint did not receive any LIM-n designation, and the existence of the very little-known XLIM-99A and XLIM-100A designations, allocated by the U.S. Army in 1972. Whether one or both of the LIM-99-100 designators is related to the Spartan and-or Sprint missiles, I don't know.

Specifications

Note: Data given by several sources show slight variations. Figures given below may therefore be inaccurate!

Kwajalein The US military base located on this Pacific island group has major tracking facilities and is near the impact area for dummy warheads fired by ICBM's from Vandenberg AFB. It is a key test location for anti-ballistic missile systems. More...